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NASA's Hubble Space Telescope photographed three magnificent sections of the Veil
Nebula  the shattered remains of a supernova that exploded thousands of years ago.
This series of images provides beautifully detailed views of the delicate, wispy structure
resulting from this cosmic explosion. The Veil Nebula is one of the most spectacular
supernova remnants in the sky. The entire shell spans about 3 degrees on the sky,
corresponding to about 6 full moons.

The Veil Nebula is a prototypical middle-aged supernova remnant, and is an ideal
laboratory for studying the physics of supernova remnants because of its unobscured
location in our Galaxy, its relative closeness, and its large size. Also known as the
Cygnus Loop, the Veil Nebula is located in the constellation of Cygnus, the Swan. It is
about 1,500 light-years away from Earth.

Stars in our Galaxy, and in other galaxies, are born and then die. How long a star lives
depends on how massive it is. The more massive the star, the shorter its life. When a
star significantly more massive than our Sun runs out of fuel, it collapses and blows
itself apart in a catastrophic supernova explosion. A supernova releases so much light
that it can outshine a whole galaxy of stars put together. The exploding star sweeps
out a huge bubble in its surroundings, fringed with actual stellar debris along with
material swept up by the blast wave. This glowing, brightly colored shell of gas forms a
nebula that astronomers call a "supernova remnant."

Such a remnant can remain visible long after the initial explosion fades away. Scientists
estimate that the Veil supernova explosion occurred some 5,000 to 10,000 years ago.

The small regions captured in these Hubble images provide stunning close-ups of the Veil.
Fascinating smoke-like wisps of gas are all that remain visible of what was once a star in
our Milky Way Galaxy. The intertwined rope-like filaments of gas in the Veil Nebula result
from the enormous amounts of energy released as the fast-moving debris from the
explosion plows into its surroundings and creates shock fronts. These shocks, driven by
debris moving at 600,000 kilometers per hour, heat the gas to millions of degrees. It is the
subsequent cooling of this material that produces the brilliant glowing colors.

The Hubble images of the Veil Nebula are striking examples of how processes that take
place hundreds of light-years away can sometimes resemble effects we see around us in
our daily life. Although caused by different forces, the structures show similarities to the
patterns formed by the interplay of light and shadow on the bottom of a swimming pool,
rising smoke, or a ragged cirrus cloud.

Although only about one star per century in our Galaxy will end its life in this
spectacular way, these explosions are responsible for making all chemical elements
heavier than iron, as well as being the main producers of oxygen in the universe. Elements
such as copper, mercury, gold, and lead are forged in these violent events. The expanding
shells of supernova remnants mix with other clouds in the Milky Way and become the raw
material for new generations of stars and planets. The chemical elements that constitute
Earth, and indeed those of which we ourselves are made, were formed deep inside ancient
stars and distributed by supernova explosions in nebulae like the one we see here.

The images were taken with Hubble's Wide Field Planetary Camera 2 (WFPC2) in
November 1994 and August 1997. The color is produced by creating a composite of three
different images. The colors indicate emission from different kinds of atoms excited by
the shock: blue shows oxygen, green shows sulfur, and red shows hydrogen.